Crude oil can be classified into light oil (for example, oil that has a low density, viscosity, and specific gravity, and can flow freely at room temperature) and heavy oil (for example, oil that has higher viscosity and specific gravity than light crude oil, and that cannot flow easily). A determination of the viscosity of oil can aid in the successful recovery of the oil from oil wells. For example, Nuclear Magnetic Resonance (NMR) techniques can be used to determine the viscosity of heavy oil.
Under certain conditions, the organisms, for example, bacteria, yeasts, molds, fungi, and the like, can form various classes of compounds present in oil by processes collectively termed as biodegradation. Such biodegradation can affect the properties, for example, viscosity, of the oil.
Like reference symbols in the various drawings indicate like elements.